As air travel has increased over the past decades, airport facilities have become more crowded and congested. Minimizing the time between the arrival of an aircraft and its departure to maintain an airline's flight schedule, and also to make a gate or parking location available without delay to an incoming aircraft, has become a high priority in the management of airport ground operations. The safe and efficient ground movement of a large number of aircraft simultaneously into and out of ramp and gate areas has become increasingly important. As airline fuel costs and safety concerns and regulations have increased, the airline industry is beginning to acknowledge that continuing to use an aircraft's main engines to move aircraft during ground operations is no longer the best option. The delays, costs, and other challenges to timely and efficient aircraft pushback from airport terminals associated with the use of tugs and tow vehicles make this type of aircraft ground movement an unattractive alternative to the use of an aircraft's main engines to move an aircraft on the ground. Restricted use of an aircraft's engines on low power during arrival at or departure from a gate is an additional, although problematic, option. Not only does such engine use consume fuel, it also burns fuel inefficiently and produces engine exhaust that contains microparticles and other products of incomplete combustion. Operating aircraft engines, moreover, are noisy, and the associated safety hazards of jet blast and engine ingestion in congested gate and ramp areas are significant concerns that cannot be overlooked.
The use of a drive means, such as a motor structure, integrally mounted with a wheel to rotate the wheel of an aircraft has been proposed. The use of such a structure should move an aircraft independently and efficiently on the ground without reliance on the aircraft's main engines. U.S. Pat. No. 7,445,178 to McCoskey et al, for example, describes an aircraft ground movement system with electric nose wheel motors that work in concert with a guidance system intended to move a taxiing aircraft. This system requires ground based and other components external to the aircraft for its operation, however. U.S. Pat. Nos. 7,469,858 to Edelson; U.S. Pat. No. 7,891,609 to Cox; U.S. Pat. No. 7,975,960 to Cox; U.S. Pat. No. 8,109,463 to Cox et al; and British Patent No. 2457144, owned in common with the present invention, describe aircraft drive systems that use electric drive motors to power aircraft wheels and move an aircraft on the ground without reliance on aircraft main engines or external tow vehicles. While the drive means described in these patents can effectively move an aircraft autonomously during ground operations, a system and method of torque transmission through components of a drive system are not suggested. None of the foregoing art, moreover, recognizes the significant improvements in autonomous aircraft ground movement or drive wheel operating efficiency possible when torque is transmitted through a series of drive system components to actuate an aircraft drive wheel system drive means to move the aircraft during ground operations.
The drive means currently proposed for aircraft drive wheel drive systems to drive aircraft autonomously on the ground may rely on gearing systems that operate with the drive means to drive an aircraft wheel and, thus, the aircraft. The replacement of gears by traction drives has been suggested in non-aircraft contexts. Adapting roller or traction drive systems to replace gearing and/or gear systems in aircraft drive wheel drive systems that actuate drive means to independently drive an aircraft drive wheel has not been suggested, however. Additionally, neither providing a clutch assembly to activate such roller traction drive systems nor providing a system for transmitting torque through components of an aircraft drive wheel drive system have been mentioned in the art. While the use of a torque arm assembly in combination with a clutch to provide controlled release of a load is described in U.S. Pat. No. 7,987,960 to Stoltze, this system anticipates load sharing among multiple torque arm assemblies in a backstopping clutch arrangement that is also used to prevent reverse rotation of system components. Such a system would not effectively transfer torque in an aircraft drive wheel drive system, however.
A need exists, therefore, for a system for transferring torque during operation of an aircraft drive wheel drive system that effectively transfers torque through the drive system components when a drive system-actuated drive means is actuated to drive an aircraft drive wheel to move the aircraft autonomously on the ground without reliance on the aircraft's main engines or external ground vehicles.